Within Doors
by Lomonaaeren
Summary: Slight AU, taking place during HBP. It takes three detentions for Severus Snape to realize why Harry Potter cleans cauldrons so well-and even more for him to decide what to do about it. COMPLETE.


**Title:** Within Doors  
 **Disclaimer:** J. K. Rowling and associates own these characters. I am writing this story for fun and not profit.  
 **Pairings:** None, gen  
 **Content Notes:** Angst, mild AU, present tense  
 **Rating:** PG  
 **Wordcount:** 2200  
 **Summary:** It takes three detentions for Severus Snape to realize why Harry Potter cleans cauldrons so well—and even more for him to decide what to do about it.  
 **Author's Notes:** An Advent fic requested by jtsbbsps_dk, who asked for the fic that's in the plot summary. This story takes place in Harry's sixth year.

 **Within Doors**

"Get to the scrubbing, Potter."

Potter says nothing, but walks over to the first of the stubborn, scratched, stained set of cauldrons that Severus has prepared for him. Severus smiles down at the essay he's marking. Not that the essay deserves it, but his plan for Potter does. He'll spend all evening working on those cauldrons, trying to get out the particular nightmare that's the mixture of powdered bicorn horn with purple lichen, and he won't finish, and he'll have to come back tomorrow night.

It's the least he deserves for being the "Potions prodigy" that Horace claims he's turned into, and for his cheek in Defense.

The boy silently runs water, picks up brushes, shifts cauldrons around. Severus becomes exercised with the poor grammar of this particular set of essays and doesn't pay him a great deal of attention. But he knows that not nearly enough time has passed when Potter steps away from the cauldrons and says, "I'm done, sir."

Severus stares at him in shock. Potter gives him a strange expression back. He's not smirking or laughing. He just looks—weary, but relaxed. As if he's been practicing dueling and achieving something.

Severus stands and storms over to the cauldrons. A scathing retort to Potter's stupid words is on his tongue as he casts a _Lumos_ Charm that will let him see into the dim corners of his office better.

The retort dies as he stares into the cauldrons and sees that they're gleaming. And not scraped the way they would have been if Potter tried a Scouring Charm on them, either. It simply looks as if Potter attacked them with hot water and wire scrubbing brush and really got the stain off.

That's impossible, though. Not impossible _per se_ , but in the amount of time he had.

By the time Severus turns around to flay Potter, he's gone.

* * *

Of course, that gives Severus the excuse to assign Potter another detention. And this time, he has the cauldrons from his largely failed first-year Gryffindor-Slytherin class ready. Even the Slytherins didn't watch their fires carefully enough, and now there's a gummy mess of newt eyes clinging under the lip of every cauldron.

Severus watches Potter this time. Potter doesn't flinch when he sees the teetering stacks of cauldrons waiting for him, or smells the stench rising from them. In fact, he only looks slightly pleased. He rolls up the sleeves of his old uniform robe, grabs the brush he used last time, and then drags the first cauldron towards the water.

Severus continues watching. Potter simply dips the brush into the water and begins to scrub.

And it seems as though that is all there is to it. Severus changes his angle several times, using the excuse of walking to the shelves to procure a book or an ingredient, but he can't catch a spark of wandless magic. Potter watches the cauldrons and doesn't seem to notice his movements, although most of the time in the classroom, he tenses the minute Severus shifts his weight.

It is a mystery.

Severus does not like mysteries. They tend to lead to things like the Dark Lord hiding on the back of a professor's head, or a monster paralyzing students. But as he watches, the greatest mystery he sees is the little flick Potter gives his wrist when he reaches the end of a particularly stubborn line of newt eyes, which evidently softens them and gets them out of the way. And when the newt eyes fall on the floor or into the cauldron, Potter dives after them and picks them up with no sign of disgust.

Even Severus would not do that. Newt eyes are uniquely bulging and slimy.

Potter finishes the first cauldron and sets it aside. And moves on to the next. And the next. His movements are gentle and relentless, and the few times that Severus gets a glimpse of his face, he has a small smile.

But not a big one, and not one that Severus can justify assigning detention because of. Nor can he fault Potter on the cleanliness of his cauldrons. They are perfection, probably better, some of them, than when they came from the maker.

"Dismissed," he says crossly.

Potter's shoulders hunch up again at once, and he leaves the office with his head bowed in a way that doesn't seem meant to conceal a smile. Severus stares after him, wondering why the end of detention should make Potter more upset than the detention itself did.

* * *

Severus does ask a few of the other professors to find out whether Potter likes to clean for them, as well, but it's useless. Most of them don't assign the same kind of detention as Severus, since they don't have equipment to clean. Rolanda is the sole exception, and Potter's never received detention with her. There's Filch, but he always tromps away to see about something in the castle when he has people serving detention, so Potter could have made faces or used magic and he'd never know.

Watching Potter at meals and in class and walking through the corridors does not work, either. There are always those subtle lines of tension that Severus only saw _return_ when Potter walked out of the detention. He laughs with his friends and eats his meals and studies his books, but he does it with his shoulders lifted around his ears, waiting for the next blow to fall.

Severus has to accept, begrudgingly, that this may be one of these minor mysteries that are never destined to be solved.

But the "begrudgingly" is still stronger than the "never destined to be solved" when he gives Potter detention for threatening Malfoy in Defense, and this time, he's prepared.

* * *

"Tell me how you would scrub these cauldrons."

Potter twitches his head to look at him, and then stops, probably because Severus is standing behind his desk with his arms folded instead of seated. "Sir?" he asks, visibly uneasy.

"I want to know how you would scrub the cauldrons, without you actually doing it. Describe to me your _process._ " Severus can't avoid a sarcastic inflection on that last word, and from the flinch Potter gives next to him, he hears it, too. But he only goes on staring at Severus as if this doesn't make sense at all.

"I've not got all night, boy," Severus finally barks, and that makes Potter stumble into speech.

"I'd run the water hot, as hot as I could stand it. I'd make sure that the brush gets soaked, and that I find the best angle to attack the stains from. Then I'd scrub as hard and as long as necessary to soften the slime. Or get the stain off, whichever it is."

Potter finishes. Severus stares at him. He didn't expect a confession of using accidental magic—the boy is too proud and arrogant to confess such a thing—but he expected more than—this.

"That is too simple."

"Too simple in what way? Sir." Potter adds the word quickly, keeping one eye on Severus as if he assumes that he's about to come out from behind the desk and smack Potter across the head. Severus frowns and takes a step backwards. Potter might bolt like a rabbit if he frightens him too badly, and then Severus will never get his answers.

"You have used magic. You _must_ have used magic."

"No, sir."

"There is no way that you came to this school knowing how to scrub stains that defeat even NEWT students," Severus tells him harshly. "So it must have been magic."

"My aunt taught me how to scrub, sir."

Severus stares at him again. It's true that a Muggle woman would know more of Muggle methods of cleaning than any witch or wizard, but Severus still can't understand _why_ she would have taught Potter this particular skill. "She knew this was a common detention?"

"No, sir."

Severus seethes internally when he realizes that Potter intends to offer him no more than that. He stalks around the desk, and Potter backs up, without a trace of the relaxed demeanor and small smile that Severus has seen every time he could attack the cauldrons. It irritates Severus, although he does not know why.

In any case, he has bigger game to hunt at the moment. "Why did she teach you that, Potter?"

"She wanted me to know it. Sir."

The insolence is too close to outright spoken words for Severus's taste. He shakes his head. "You expect me to believe that your aunt wanted the celebrate Boy-Who-Lived to do menial work?"

"She always said I should know how to do it. I know she thinks magic can't take care of everything."

Severus pauses in irritation again. That is the truth. He can feel that with the passive Legilimency that always detects lies. But it is not the whole truth. Even though it sounds like it. Even though it _feels_ like it.

This isn't Legilimency he's using to feel that. Just sheer knowledge of Potter. Potter-intuition, he could call it, if he was in the habit of fixing soppy names on things.

He shakes his head again. "I do not believe you."

"You could owl my aunt, Professor."

"You will _tell_ me, Potter." And Severus does something he does not often do. He incants _Legilimens_ nonverbally and uses it to dip below the surface of Potter's thoughts, much deeper than he usually does with students whose lies he wants to penetrate.

It's chaos, which is expected. The _last_ thing he expects is to find an image of Potter scrubbing dishes with bleeding, scalded hands, while Petunia Evans stands over him and screeches at him, "As hot as you can get it! Always! And you'll scrub until my Duddykins has a clean plate to eat off!"

Severus staggers back from a sudden blow. He thinks at first that Potter must have shoved him, either actually or with accidental magic, and has a scathing retort forming on his tongue, until he realizes that it came from actual Occlumency. Potter is desperate to keep him out of his mind.

So desperate that he turns and runs. Severus is left staring at the door, with a truthful image in his mind and echoes ringing in his brain.

He should not have done that. But he needed to know.

* * *

It's simplicity itself to pull Potter in for another detention, of course. Even Albus shakes his head gravely over the thought of the boy running out of one. "I had hoped that you might get along better before I had to leave matters in your hands, Severus," he sighs, and looks down at the blackened, cracking skin that Severus has only arrested temporarily. "I hoped you would understand each other."

Severus does not retort that he understands the boy much better now. There are some secrets he means to keep.

When Potter arrives, he keeps his head averted. Severus stands in front of his desk with arms folded and stares at him. "Am I writing lines, sir?" Potter asks, keeping his head down.

"No. You are going to brew the potion that you were too busy helping Granger in class today to do properly."

Potter jerks his head up and stares, as if he wonders how Severus heard about that from Slughorn. Severus looks back with his blandest, blankest mask, and pivots his head towards the ingredients lying chopped on the student desk he's placed in his office. Potter swallows, then moves slowly towards them.

Severus watches him narrowly. Potter is competent enough when he doesn't think anyone is going to take points. He shreds leaves, he watches brewing times, he tucks his wand away and doesn't reach for it even when he has to add a few quick pinches of dried hawthorn flowers in order to keep the potion from exploding. But there's no joy in it, no relaxed half-smile. It's thin, brittle duty.

Severus looks at the potion in the vial, when Potter is done and Severus has dismissed him, for a long time.

* * *

"Sir?"

That's Potter, wide-eyed before a stack of cauldrons with glittering, oozing liquid in them that still emits occasional bangs. Severus doesn't bother to look up from the stack of essays he has to finish.

"Your friends the Weasley twins _do_ find innovative ways to cause chaos even when they no longer attend this school," he says, with a lazy wave of his hand. "Clean this out. It's going to take especially hard scrubbing this time."

Severus keeps his head down. There's silence for long enough, without the sound of breathing, that he thinks Potter may even have gone away.

But then there's footsteps. And the sound of hot running water. And the smell of steam. When Severus permits himself a glance up exactly five minutes and five seconds later, he surprises the tiny half-smile on Potter's face as he bends over and begins to address himself earnestly to the steam.

Severus sighs a little and turns his own attention on the essays. He's given Potter as much as the boy can take from him, right now. A little bit of peace, in the middle of the duty that consumes both of them.

For as long as he can.

 **The End.**


End file.
